Abstract
Objective: This study aimed to evaluate psychotropic drug utilization among inpatients in a tertiary care hospital over a one-year period using the Anatomical Therapeutic Chemical/Defined Daily Dose (ATC/DDD) methodology.

Methods: A retrospective, cross-sectional drug utilization study was conducted in a tertiary care hospital in Türkiye. All psychotropic medications prescribed for inpatient use between 1 January and 31 December 2024 were included. Drug consumption data were obtained from the hospital information management system and classified according to the WHO ATC system. Utilization was expressed as defined daily doses per 100 bed-days (DDD/100 bed-days).

Results: A total of 443,606 psychotropic medication units, comprising 37 active substances and 82 pharmaceutical formulations, were analyzed. The overall psychotropic drug consumption rate was 87.49 DDD/100 bed-days. Psycholeptics (ATC N05) constituted the largest therapeutic group, accounting for 88.78% of total consumption. Midazolam was the most frequently utilized psychotropic agent, reflecting substantial use in non-psychiatric inpatient settings. Selective serotonin reuptake inhibitors (SSRIs) represented the predominant antidepressant class. Although atypical antipsychotics accounted for a higher proportion of total DDD consumption than typical agents, no statistically significant difference was observed between the two groups.

Conclusion: This study provides a comprehensive overview of inpatient psychotropic drug utilization in a tertiary care hospital setting. The findings highlight the predominance of psycholeptics and underscore the influence of non-psychiatric clinical practices on overall consumption patterns. These results offer a valuable reference for monitoring prescribing trends, supporting rational drug use, and guiding future multicenter pharmacoepidemiological studies in Türkiye.

Key words: ATC/DDD methodology, Drug utilization, Inpatients, Tertiary care hospital, Türkiye